1. Field of the Invention
This application relates to an image reading device configured to read an image recorded on a sheet material, e.g., a document sheet.
2. Description of Related Art
A known reading device, e.g., a scanner, comprises a platen glass, a document cover, and an image sensor, e.g., a contact image sensor (CIS) and a charge coupled device (CCD). The platen glass has a document holding portion. The image sensor is disposed at a lower surface of the platen glass. The document cover is configured to cover a document sheet placed on the document holding portion. The known reading device further comprises an automatic document feeder (ADF) that is disposed in the document cover and is configured to take up document sheets placed on a document tray, one at a time, and automatically feed a document sheet to an image reading position.
In a flat-bed mode in which the ADF is not used, the image sensor reads an image from a document sheet placed on the document holding portion while moving along the platen glass. In an ADF mode in which the ADF is used, the image sensor reads an image from a document sheet fed by the ADF while stopping at the image reading position. The ADF comprises a transparent discharge guide member configured to guide, upward from the platen glass, a document sheet having passed the image reading position. In the ADF mode, the image sensor reads an image from the document sheet through the transparent discharge guide at the image reading position.
When the platen glass is a single glass, and the image reading position is within the document holding portion, the image sensor is configured, in the flat-bed mode, to read an image from a document sheet through the transparent discharge guide member when the image sensor passes the image reading position. In this case, if the document sheet is smaller in size than a recording sheet, the image sensor may read an extending portion of the discharge guide member from the document sheet, and the outline of the discharge guide member may appear, as black streaks, in an image read and recorded on the recording sheet. As a result, the recorded image is degraded in quality.